[Pharo-project] [COTDC] 40#2 - NonReentrantWeakMessageSend

Stéphane Ducasse stephane.ducasse at inria.fr
Tue Apr 5 20:43:18 CEST 2011


+1 


On Apr 5, 2011, at 8:29 PM, laurent laffont wrote:

> Thanks a lot Henrik.
> 
> Laurent.
> 
> On Tue, Apr 5, 2011 at 12:02 PM, Henrik Johansen <henrik.s.johansen at veloxit.no> wrote:
> NonReentrantWeakMessageSend does what it says, while the message is being executed, additional evaluations will be discarded.
> It's used by when:sendOnce:to: protocol from Polymorph events, but unused in the base image.
> when:send:to:exclusive: is used one place though.
> 
> It's useful when objects are mutually registered to each other's events, but the actions may lead to the others action being triggered.
> Examples are 
> - two lists whose contents update based on the selection in the other
> - The DiffMorph (Uses ExclusiveWeakMessageSend)
> 
> ExclusiveWeakMessageSend are used when the decision whether to process an event is shared between multiple objects.
> IE 2 objects respond to different events, but if received simultaneously, only the first of them should have it's action executed.
> 
> With Announcement, the corresponding functionality to non-reentrancy would be achieved using:
> VW - AnnouncementCollection>>suspendWhile:  anActionBlock
> Pharo - Announcer >> suspend: aSubscriber while: anActionBlock (As we neither have a specific AnnouncementCollection class, nor access to Registry itself. Not implemented yet though :P)
> 
> The shared state required to achieve Exclusivity would probably have to recide outside of the framework.
> 
> Cheers,
> Henry
> 
> 
> On Apr 4, 2011, at 9:59 56PM, laurent laffont wrote:
> 
>> Today:  NonReentrantWeakMessageSend
>> 
>> 
>> (ExclusiveWeakMessageSend aborted - no answer)
>> 
>> 
>> Comment Of The Day Contest - One Day One Comment
>> Rules: 
>> #1: Each day a not commented class is elected. Each day the best comment will be integrated with name of the author(s).
>> #2: If you cannot comment it, deprecate it.
>> Results: http://code.google.com/p/pharo/wiki/CommentOfTheDayContest
>> 
>> Laurent
> 
> 




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